The present invention relates to a domestic washing machine equipped with an electrochemical cell which is capable of generating chlorine gas to be dissolved in water and then to be sent to a washing tub of the machine for achieving a bleaching operation of the laundry therein. The present invention further relates to such a washing machine additionally equipped with a decalcifier or water softener to soften water which is to be used in various stages of the washing cycle.
Known in the art is a washing machine which is equipped with an electrochemical cell capable of producing sodium hypochlorite for achieving bleaching of the laundry, as well as with a decalcifier for softening system water before introduction into the washing tub, and with a salt tank which is supplied with salt, i.e. sodium chloride, and which is fed with system water in order to produce brine.
In such prior art machine, the salt tank can be connected selectively by means of suitable valves either with the electrochemical cell in order to send brine mixed with the system water to the cell, thereby to generate therein sodium hypochlorite by electrolysis, or with the decalcifier in order to regenerate the internal ion exchange resins therein during an operation of regeneration of the decalcifier, thereby to enable the decalcifier again to be able to soften the system water. By this machine it therefore is possible directly to generate sodium hypochlorite to be introduced into the wash tub diluted with water in predetermined proportions at specific stages of the operating program of the machine to achieve a bleaching operation of the laundry and to use detergents of simpler composition which pollute less compared with conventional detergents.
However, although this type of machine operates satisfactory and reliably, such washing machine has certain inherent disadvantages due primary to the provision of the electrochemical cell.
In fact, in order to achieve effective bleaching of the laundry, the electrochemical cell must generate relatively consistent amounts of sodium hypochlorite. However, such actually does not occur due to the construction of the cell necessary to enable a compact machine structure. Thus, the amount of sodium hypochlorite generated during the periods in which the cell is operating is inadequate for the purpose intended. Therefore, in this type of washing machine, the optimal condition required for satisfactory bleaching can be obtained only by using an electrochemical cell of relatively large overall dimensions, particularly horizontally. Such dimensions however, make it difficult and expensive to provide such a cell in the washing machine.
Furthermore, the performance of the electrochemical cell which generates sodium hypochlorite, depends, as is known, on the operating temperature of the cell itself. In particular, in the temperature is slightly above ambient temperatures during electrolysis, the cell will produce relatively smaller amounts of sodium hypochlorite due to the formation of additional compounds, such as chlorates, etc., which have oxidation capabilities higher than sodium chlorite and which therefore are ineffective from the standpoint of achieving bleaching. To prevent the occurrence of such higher temperatures, it would be necessary to cool the cell by means of conventional cooling devices. However, the provision of such cooling devices would further complicate the construction of the machine and would be economically prohibitive.
Still further, the sodium hypochlorite solution which is generated by this type of electrochemical cell contains significant amounts of sodium chloride which, upon entering the washing tub, cause undesirable corrosion of the metallic materials of the tub.